In wireless communication networks, common network topologies are that of a star or a cluster. In a star network, all terminal nodes communicate with each other via a central node called a coordinator. The coordinator receives signals from transmitting nodes and forwards the signal to receiving nodes. In a cluster network, all terminals communicate directly with each other. In both star and cluster networks it is still necessary to enforce a channel access methodology in order to efficiently utilize the network bandwidth. The main purpose of the coordinator is to determine and broadcast a channel access schedule to the network terminals.
There is a need for a heterogeneous network because of the large number of disparate radio devices that can use a given frequency band. This is clearly a problem in unlicensed radio frequency bands. In the United States, unlicensed bands are known as ISM, and are centered around 2.4 GHz and 5 GHz. In the rest of the world, similar bands are used.
In the 5 GHz band, for example, radio terminal can conform to various IEEE 802 standards. Ultra-wide bandwidth (UWB) terminals may not conform to any standard. Enabling a coordinated channel access mechanism for such terminals could improve bandwidth utilization by reducing interference. More importantly, the cost of the terminals can be reduced if for some applications only a simple low bit rate radio is needed to satisfy the communication bit rate requirements. Then, an existing high-speed network, such as the one defined in the IEEE 802.15.3a standard, could incorporate cheaper low bit rate terminals and offer coordination and channel access services. Such a scenario would eliminate the need for a separate network for low bit rate terminals.